The production of thermoplastic sheet reinforced with fiberglass mat is receiving considerable attention because of the expected economics in forming high strength, dimensionally stable parts from such a structure. To make the sheet, layers of fiberglass mat are impregnated with molten polymer in either a batch or continuous fashion. A variety of polymers or blends can be used as the matrix for the sheet, with polyolefins and polyesters being the materials of greatest interest. Polyesters, such as poly(ethylene terephthalate) (PET), are preferred for applications where high heat resistance is required. A key property of all these compositions is the impact strength, which desirably is as high as possible, but it is also important to maintain high heat resistance and good formability.
We are familiar with a number of patents dealing with reinforced thermoplastic sheet. Patents of interest include U.S. Pat. Nos. 3,664,909; 3,684,645; 4,277,531; 4,335,176; 3,713,962; 3,883,888; 3,850,723 and European Applications Nos. 86113362.7 and 86113363.5. Other patents include U.S. Pat. Nos. 4,263,364; 4,379,802; and 4,699,942.